I bought my old 94' back and it's running poor. I talked with Jerry and he is thinking it's a fuel sending unit on the secondary side of things. Car runs fine with the key off, but craps all over itself when I turn the key.

I took it to a shop in Tulsa and after 5 weeks or so I just picked it up as they couldn't fix it. So I need some help getting her running strong.

I bought my old 94' back and it's running poor. I talked with Jerry and he is thinking it's a fuel sending unit on the secondary side of things. Car runs fine with the key off, but craps all over itself when I turn the key.

I took it to a shop in Tulsa and after 5 weeks or so I just picked it up as they couldn't fix it. So I need some help getting her running strong.

Anyone know who I could call or take it to?

Thanks,

Joe

Jerry (I'm sure) is referring to the secondary fuel pump as a possibility and a place to start.

I would suggest that you put a fuel pressure gauge on the Schrader valve and with the ignition key OFF measure the current between the (POS) battery terminal and the (red wire/black connector) diagnostic connector (jutting out of the big wire loom near the wiper motor).

Doing this will energize BOTH fuel pumps resulting in a pressure reading near 50 psi or so. And, if both pumps are running, the current draw will be 8 to 10 amperes, normally. (A reading of half that indicates one of the pumps is NOT working - I'd guess the secondary pump too, in that case.)

If not a fuel pressure issue, then its onto measuring the resistance of the injectors -

These are elementary steps that I would expect any shop should have done. But, then again, I don't EVER take my Zs to ANY shop because there's a good chance none of their "mechanics" have ever seen an LT5, let alone worked on one.

Come join us in the ZR-1 Registry too. Lots of talent there and a chance to find someone close enough to you to lend a hand.

Paul wrote up a very good trouble shooting guide. The only thing I would add is to pull the FP2 (Fuel Pump 2) fuse to test the primary pump alone and then reinstall FP2 but pull FP1 to test the secondary pump alone. This will narrow down exactly which pump is the problem...like Jerry and Paul, I suspect the secondary fuel pump too. Let us know what you find.

I'm guessing maybe a secondary vacuum hose leak. When you start up the engine, listen for the secondary vacuum pump near the passenger side headlight. It should shut off after a few seconds. If it keeps running you probably have a vacuum hose leak
Mine used to stumble with the power key turned on and ran fine with it off. Was a vacuum leak

I was told by someone on this forum about John Conover near Okla City.
He is the GM C4 certified ZR1 mechanic at Hudiburg Chevrolet on I 40 in Midwest city Ok...Phone #.405 737 6641''''
I'm having a problem with mine and thinking of taking it to him.
I have spoken with doc on 11th St Tulsa [OK fellow] but he did not seem to have much knowledge of the C4 ZR1.
Good luck with yours. would you lets us on the forum know when you get it solved. Thanks

This is kind of a walk of shame post being that it's been a year and half, BUT we finally got it fixed. Long story short is we replaced anything and everything we could think of and nothing worked. I was a week away from shipping the car to Mark in Chicago when a shop called me back that couldn't get me in two months before. I told him he had 5 days to figure it out and he said he would like a shot at it. At the end of the day the shop had the capability to program the chip and took information from it and work backwards to figure out what was going on. As embarrassing as this is to say it turns out to be a fuse connected to the O2 sensors!!! One of the first things we replaced on our own were the O2 sensors w/o any luck. Had no idea that the fuse was busted. The computer was getting a bad reading until the exhaust heated up and would make the car stumble. So after 3 shops, more then a year of chasing the problem, and $3,500 of parts and shop fees it turned out to be a $1 fuse.

It's nice to have it running strong again. Still a fantastic and fun car to drive after 20 years of ownership!

This is kind of a walk of shame post being that it's been a year and half, BUT we finally got it fixed. Long story short is we replaced anything and everything we could think of and nothing worked. I was a week away from shipping the car to Mark in Chicago when a shop called me back that couldn't get me in two months before. I told him he had 5 days to figure it out and he said he would like a shot at it. At the end of the day the shop had the capability to program the chip and took information from it and work backwards to figure out what was going on. As embarrassing as this is to say it turns out to be a fuse connected to the O2 sensors!!! One of the first things we replaced on our own were the O2 sensors w/o any luck. Had no idea that the fuse was busted. The computer was getting a bad reading until the exhaust heated up and would make the car stumble. So after 3 shops, more then a year of chasing the problem, and $3,500 of parts and shop fees it turned out to be a $1 fuse.

It's nice to have it running strong again. Still a fantastic and fun car to drive after 20 years of ownership!

Sorry for taking forever getting back.

Congrats on finally getting it fixed. Can you tell us the name of the shop? Itís always good to know a quality shop no matter where. Exactly what fuse was it they replaced? Inquiring minds want to know.
Hope you use the car in good health.
H

It seems that the same fuse that powered the vacuum pump for the secondary intake runner valves, the O2 sensor heaters, and the power key blew. The vacuum pump motor seized and blew the fuse and cause the O2 sensors to give inaccurate readings to the computer.

The shop that fixed it is in Broken Arrow, OK. The guys name is Randy and has a shop behind his personal home.

It seems that the same fuse that powered the vacuum pump for the secondary intake runner valves, the O2 sensor heaters, and the power key blew. The vacuum pump motor seized and blew the fuse and cause the O2 sensors to give inaccurate readings to the computer.

The shop that fixed it is in Broken Arrow, OK. The guys name is Randy and has a shop behind his personal home.

Later

Glad you got it sorted out Joe. Iím sorry I wasnít able to do more for you.
Ironically, I had the same problem, blowing fuse on SPT vacuum pump. After trying to chase down the short, I just finally removed the SPT system completely, something I was always planning to do. Never thought about the pump being locked up.
Drop by & see me sometime. We go to T-town frequently so maybe we can get together!
jerry